Objective: To determine whether older drivers with poorer cognitive and/or visual function drive fewer miles or avoid driving in situations that pose higher crash risks, such as at nighttime, in rush hour traffic, or when weather conditions are bad.
Design: A cross-sectional data analysis conducted as part of a larger prospective study.
Subjects: A total of 3238 drivers aged 65 and older applying for renewal of their driver's license at one of eight participating North Carolina driver's license offices.
Measurements: Subjects were administered a battery of brief tests of cognitive and visual function, which included the Trail Making Test Parts A and B, the Short Blessed Orientation-Memory-Concentration test, and measures of high and low contrast visual acuity, contrast sensitivity, and peripheral vision. Participants were also asked to complete a brief driving survey containing questions about the number of miles they drove and whether they avoided driving under certain conditions, such as after dark or on busy, multi-lane roadways. Driver age and gender were covariates in the analyses.
Results: Results of multivariate logistic regression models show a clear pattern of reduced driving exposure--lower annual miles and greater avoidance of high-risk driving situations--associated with lower levels of cognitive and visual function. In general, the prevalence odds of reduced driving exposure were higher for the cognitive function variables than for the visual function variables, and higher for males than for females. Men who scored in the lowest quartile of performance on one of the cognitive tests were six to seven times more likely to report driving fewer than 3000 miles a year than were men scoring in the highest quartile, and women with low scores were one-and-one-half to two times more likely to report driving less than 3000 miles than women with higher scores.
Conclusions: While the findings of this study are reassuring, they do not guarantee that all drivers with cognitive and visual impairments are limiting their driving exposure appropriately, and geriatricians and other health professionals should be encouraged to evaluate their patients' cognitive and visual fitness for driving and provide counsel where indicated.